Expansion-drill.



i PATENTED JAN. 21 1908.

J. B. TYGART.

EXPANSION DRILL.

APPLICATION FILED SEPT. 11. 1907.

Q; In cows attuned:

TMEYNORRIS PZTIRS cm, WASHINGTON, n. c.

JAMES B. TYGART, OF WHITWELL, TENNESSEE.

EXPAN SIGN-DRILL Specification of Letters Patent.

Patented Jan. 21, 1908.

Application filed September 111 1907. Serial No. 392.400-

T 0 all whom it may concern:

Be it known that 1, JAMES B. TYGART, a citizen of the United States, residing at Whitwell, in the county of Marion and State of Tennessee, have invented new and useful Improvements in Expansion-Drills, of which the following is a specification.

This invention relates to improvements in coal and other mining drills having extensible or expansion bit ends or cutters for enlarging the inner end of the drill bore to receive the blasting charge, the object of the invention being to provide an expansion drill of novel construction whereby the operation of enlarging a drill bore may be conveniently and expeditiously performed.

The invention consists of the features of construction, combination and arrangement of parts hereinafter fully described and claimed, reference being had to the accompanying drawing, in which Figure 1 is a side view of an expansion drill embodying my invention, with the expansion cutters separated for use. Fig. 2 is a similar view, showing the expansion cutters retracted for inserting and removing the drill. Fig. 3 is a section on'line 3-3 of Fig. 2.

Referring to the drawing, the numeral 1 designates a drill of the usual spiral form, which is provided at its forward end with a short flat tang or shank 2. From the tang 2 is supported a head 3, preferably comprising a flat metallic casting of generally rectangular form, and provided at its outer end with a socket 4 to receive the tang 2, which may be secured therein in any preferred manner, as by the use of one or more rivets 5.

The head 3 carries a pair of cutting blades or bits 6 and 7 which have their forward or cutting ends curved in opposite direction, as clearly shown in Fig. 3, said ends being beveled to cutting edges and each bifurcated to form a pair of cutting points 8. The blades 6 and 7 are integral with short shanks 6 and 7 extending from their inner or rear ends, which shanks extend within a socket or recess 9 formed in the head 3 in advance of the socket 4 and separated therefrom by a'strengthening web 10. Both sockets extend transversely of the head, but the socket 9 is of greater depth than the socket 4 to provide for the reception of the shanks 6" and 7 in overlapping relation. The said shanks are pivotally mounted within the socket 9 to permit the bits or blades to swing in a directiontransversely of the tool upon a common pivot bolt 11 passing through the head and provided with a securing nut 12 by which the blades are detachably secured in position, allowing them to be removed when occasion requires for sharpening. The blades 6 and 7 extend obliquely in opposite directions relative to each other and to their respective shanks, so that when the blades are retracted or folded inwardly, as shown in Fig. 2, the shanks will lie in the line of the axis of the tool while the blades will overlap in divergent relation, By this means the blades when limited by the engagement of the shanks with the side walls of the socket 9, will project obliquely beyond the sides of the head to a maximum degree, thus allowing a bore of comparatively large diameter to be formed without the necessity of employing a head 3 of greater width than the width of the drill 1.

After a bore has been formed by an ordinary cutting drill in the customary manner, the expansion drill is inserted with the blades retracted, as shown in Fig. 2, until the outer ends of the blades come in contact with the inner end wall of the bore, when said blades will spread outward or expand under the pressure upon the drill and form, in the operation of the tool, a pocket of increased diameter at the end of the bore. When the tool is withdrawn the blades by contact with the wall of the bore proper will fold automatically back to normal position, as will be readily understood.

It will be apparent that by'providing a detachable head 3 forming a carrier for the expansion blades, blades of different sizes may be applied to the drills and used interchangeably in connection with ordinary drill bits.

Having thus described the invention, what I claim is In an expansion bit for drills, the combination of a drill having a flattened tang, a head provided with front and rear recesses, both extending transversely thereof, the rear recess receiving the tang, means for securing the tang in position, a pivot bolt carried by the head and projecting through the front recess therein, and a pair of relatively divergent expansion blades having outer cutting ends, said blades being provided at their inprojecting laterally to their fullest extent,

ner ends With integral shanks arranged 0btracted the shanks Will lie in lapping relation 10 liquely thereto, the shanks being pivoted in in the line of the axis of the tool.

overlapping relation Within the recessfor lat- In testimony whereof I afliX my signature eral svvmginlg movement solely upon the in presence of two Witnesses.

aforesaid bo t and having plane side edges,

the construction being such that When the JAMES TYGART' blades are extended the outer plane side Witnesses: edges of the shanks will engage the side Walls J. O. EALY, of the recess, While When the blades are re- W. E. MOCURRY. 

